Trafficking of sulfated glycoprotein-1 (prosaposin) to lysosomes or to the extracellular space in rat Sertoli cells

Cell and Tissue Research
S A IgdouraC R Morales

Abstract

Sulfated glycoprotein-1 (prosaposin) exists in 2 forms: a 65kDa form targeted to lysosomes and a 70kDa form secreted extracellularly. In order to understand the sorting and targeting mechanisms of the two forms of SGP-1, we have compared their maturation, processing, and secretion in rat Sertoli cells in vivo. Metabolic labeling experiments in vivo demonstrated that the 65kDa form is synthesized first, then post-translationally modified to the 70kDa form of SGP-1. Subcellular fractionation of testicular homogenate was used to obtain Golgi fractions containing up to 50-fold enrichment in galactosyltransferase. Permeabilization of enriched Golgi fractions with saponin released the 70kDa form, but did not affect the 65kDa protein. While excess free mannose 6-phosphate did not release lysosomal SGP-1, it released the 35kDa cathepsin L from Golgi membranes. Using quantitative electron-microscopic immunocytochemistry, the lysosomal contents of SGP-1 were shown to increase significantly after the administration of tunicamycin in vivo. Therefore, the trafficking of the 65kDa form of SGP-1 to the lysosomes appears to be independent of the M6P-receptor pathway. The 70kDa form of SGP-1 was found to aggregate within perforated Golgi fracti...Continue Reading

Citations

May 4, 2001·Molecular Reproduction and Development·C R MoralesS Lefrancois
Jan 23, 1999·The Biochemical Journal·L Madar-ShapiroM Horowitz
Oct 31, 2003·Biology of Reproduction·Matthew D AnwayLouis Hermo
Aug 13, 2011·Experimental Cell Research·Libin Yuan, Carlos R Morales
Jul 6, 2004·Molecular Reproduction and Development·Jibin ZengCarlos R Morales
Dec 6, 2003·The EMBO Journal·Stephane LefrancoisCarlos R Morales
Aug 2, 2007·Traffic·Stéphane Lefrançois, Peter J McCormick
Aug 14, 2012·Molecular Genetics and Metabolism·Maria Francisca CoutinhoSandra Alves
Jun 2, 2012·Molecular Genetics and Metabolism·Rafael J TamargoEllen Sidransky
Jul 17, 2004·The Biochemical Journal·Madanan Madathiparambil GopalakrishnanAndrej Hasilik
Jun 24, 2004·The Journal of Biological Chemistry·Volkan SeyrantepeAlexey V Pshezhetsky
Feb 22, 2002·The Journal of Biological Chemistry·Stephane LefrancoisCarlos R Morales
Jun 12, 2021·The Journal of Investigative Dermatology·Stephan TiedeRalf Paus

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